The present invention relates generally to gas turbine engines, and more specifically to a variable vane for use in such engines in which the vane arm is integrally engaged with the vane stem in a manner that eliminates the need for threaded fasteners, lockwashers and lockwires.
In gas turbine engines, energy is added to the air through the process of compression, while energy is extracted during combustion by means of the turbine. In a turbofan engine, compression is accomplished sequentially using a fan and thereafter using a multistage compressor; the fan and compressor being independently driven by a high pressure and a low pressure turbine, respectively, through concentric shaft connections. Combustion occurs between the multistage compressor and the high pressure turbine. Since the energy available to the turbines far exceeds that required to maintain the compression process, the excess energy is exhausted as high velocity gases through one or more nozzles at the rear of the engine to produce thrust.
Variable turbine vanes have been developed in order to regulate their relative rotational speeds. Exemplary in the art, are the systems disclosed in the following U.S. Patents, the disclosures of which are incorporated by reference:
U.S. Pat. No. 3,356,288 issued to Corsmeier; PA0 U.S. Pat. No. 3,954,349 issued to Abild; PA0 U.S. Pat. No. 4,400,135 issued to Thebert; and PA0 U.S. Pat. No. 4,214,852 issued to Tuley et al.
The references cited above disclose turbine engines with variable vane systems which regulate the rotation of the turbines. For example, Turley et al disclose a turbine vane assembly in which the vanes have variable areas. In such a system, each vane is fixed by a vane arm to its crank. All of the references disclose conventional means of attaching the arm to the crank, which include threaded fasteners, lockwashers, lockwires, and clevis pins. Since each turbine engine includes a plurality of rows of rotating turbine blades enclosed in a confined space, the initial construction and subsequent maintenance of such blades is an awkward and cumbersome process.
From the foregoing discussion, it is apparent that there currently exists a need of attaching the stator vanes of gas turbine engines to their radial crank without the use of threaded fasteners and their attendant locking mechanisms. The present invention is intended to satisfy that need.